Authorities have expanded their investigation into the fatal shooting of nine black churchgoers by a white supremacist – and more suspects could possibly face charges.

Investigators believe Dylann Roof traveled alone to Charleston – where he opened fire on a Bible study at Emanuel African Methodist Episcopal Church – and fled by himself to North Carolina, where he was captured the following day.

But authorities suspect others knew of the 21-year-old gunman’s plot, and some of them could be charged in connection with the killings, reported the Charlotte Observer.

Law enforcement sources told the newspaper that a joint state and federal investigation had widened to include persons of interest after reviewing Roof’s cellphone and computer records.

It’s not clear whether those persons of interest are friends, some of whom told reporters that Roof had talked about shooting up the College of Charleston, or organized white supremacists whose writings were cited in a manifesto attributed to the gunman.

The newspaper reported that the additional persons of interest could potentially be charged with misprision of a felony, which means that a person knew of a crime to be carried out but failed to notify law enforcement.

Other possible charges could include lying to a federal law enforcement officer, the newspaper reported.